{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31611","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-03-09T15:48:24.122Z","datePublished":"2026-04-24T14:42:32.124Z","dateUpdated":"2026-08-05T12:23:49.072Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:23:49.072Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: require 3 sub-authorities before reading sub_auth[2]\n\nparse_dacl() compares each ACE SID against sid_unix_NFS_mode and on\nmatch reads sid.sub_auth[2] as the file mode.  If sid_unix_NFS_mode is\nthe prefix S-1-5-88-3 with num_subauth = 2 then compare_sids() compares\nonly min(num_subauth, 2) sub-authorities so a client SID with\nnum_subauth = 2 and sub_auth = {88, 3} will match.\n\nIf num_subauth = 2 and the ACE is placed at the very end of the security\ndescriptor, sub_auth[2] will be  4 bytes past end_of_acl.  The\nout-of-band bytes will then be masked to the low 9 bits and applied as\nthe file's POSIX mode, probably not something that is good to have\nhappen.\n\nFix this up by forcing the SID to actually carry a third sub-authority\nbefore reading it at all."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H","baseScore":8.6,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable parser is in ksmbd, the in-kernel SMB server, and is reachable through SMB2 requests over the network.\nAC:L - A crafted security descriptor with an S-1-5-88-3 SID carrying only two sub-authorities can deterministically reach the out-of-bounds read; no race or external timing condition is required.\nPR:N - The path requires a valid SMB session and tree connection, but ksmbd supports guest/anonymous access and writable guest shares, making unauthenticated network reachability a reasonable high-severity deployment scenario.\nUI:N - No victim action is required after the attacker can connect to the SMB service; the attacker sends the crafted SMB2 request directly.\nS:U - The impact remains within the ksmbd/kernel and exported filesystem security authority, without a VM escape or separate security-domain boundary crossing.\nC:L - The bug performs a bounded 4-byte out-of-bounds read whose low mode bits can be reflected into the resulting file mode; this is a limited information exposure, not arbitrary memory disclosure.\nI:L - The out-of-bounds value is applied as POSIX permission bits, allowing constrained access-control modification of a reachable filesystem object rather than arbitrary kernel memory modification.\nA:H - The crafted read can be placed past the validated ACL/security-descriptor boundary and plausibly at the received PDU allocation edge, making a repeatable kernel oops/DoS defensible."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"],"versions":[{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","lessThan":"cf2148b880fb7c0fcd727202dbc4fd5d6998b9c2","status":"affected","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","lessThan":"b5b5d5936a50497fb151c0b122899a6894721c2b","status":"affected","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","lessThan":"08f9e6d899b5c834bbcc239eae1bed58d9b15d2c","status":"affected","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","lessThan":"d2454f4a002d08560a60f214f392e6491cf11560","status":"affected","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","lessThan":"46bbcd3ebfb3549c8da1838fc4493e79bd3241e7","status":"affected","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","lessThan":"9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a","status":"affected","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","lessThan":"53370cf9090777774e07fd9a8ebce67c6cc333ab","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/smbacl.c"],"versions":[{"version":"5.15","status":"affected"},{"version":"0","lessThan":"5.15","status":"unaffected","versionType":"semver"},{"version":"6.1.175","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.136","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.83","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.24","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"6.19.14","lessThanOrEqual":"6.19.*","status":"unaffected","versionType":"semver"},{"version":"7.0.1","lessThanOrEqual":"7.0.*","status":"unaffected","versionType":"semver"},{"version":"7.1","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.175"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.136"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.83"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.24"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.19.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.0.1"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/cf2148b880fb7c0fcd727202dbc4fd5d6998b9c2"},{"url":"https://git.kernel.org/stable/c/b5b5d5936a50497fb151c0b122899a6894721c2b"},{"url":"https://git.kernel.org/stable/c/08f9e6d899b5c834bbcc239eae1bed58d9b15d2c"},{"url":"https://git.kernel.org/stable/c/d2454f4a002d08560a60f214f392e6491cf11560"},{"url":"https://git.kernel.org/stable/c/46bbcd3ebfb3549c8da1838fc4493e79bd3241e7"},{"url":"https://git.kernel.org/stable/c/9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a"},{"url":"https://git.kernel.org/stable/c/53370cf9090777774e07fd9a8ebce67c6cc333ab"}],"title":"ksmbd: require 3 sub-authorities before reading sub_auth[2]","x_generator":{"engine":"bippy-1.2.0"}}}}